// ── Carrying out what the reconciler decided ──────────────────────────────
//
// `reconcile.plan` says WHAT a change made in the game becomes; this file writes
// it into the site's own record. Every write here is about ONE server (D190): a
// change in one game affects that server and nothing else, even when the site's
// row reaches further.
//
//   • A grant that reaches only this server is deleted or written outright.
//   • A grant that reaches more (a fleet grant, or a user's grant scoped `*`)
//     gains an EXCEPTION for this server, and keeps reaching every other one.
//   • A group shared with other servers is SPLIT: this server gets its own copy,
//     the change is made to the copy, and the shared group stops covering it. A
//     notice says so, in case the change was meant for every server.
//
// Ops are applied one at a time and each re-reads what it needs, because an
// earlier op in the same plan may have split the group a later one writes to.
// `permSync` runs a plan under one lock for the whole fleet, so two servers'
// plans never split the same shared group at once.

const db = require('./permissions.db')
const model = require('./permissions.model')

/** The site's group of this name on this server, or null (D189). */
async function groupOn(name, serverId) {
  const [groups, groupServers] = await Promise.all([db.listGroups(), db.listGroupServers()])
  return model.groupsOn(serverId, { groups, groupServers }).find((group) => group.name === name) || null
}

/**
 * The group of this name that belongs to THIS server alone, splitting a shared
 * one if that is what covers it (D190). Null when the site has no such group.
 */
async function ownGroup(name, serverId) {
  const group = await groupOn(name, serverId)
  if (!group) return null

  const groupServers = await db.listGroupServers()
  if (!model.isShared(group, model.serversByGroup(groupServers))) return group

  const copy = await db.copyGroup(group.id, 'split')
  await db.setGroupServers(copy, { allServers: false, servers: [serverId] })
  await db.removeGroupFromServer(group.id, serverId)
  await db.noteSplit(serverId, {
    group: name,
    detail: `changed in the game on ${serverId}; that server now has its own copy of "${name}"`,
  })

  return db.getGroup(copy)
}

/** The Steam ids and user linked to one Steam id, for finding a user's grant. */
async function userOf(steamId) {
  const links = await db.listLinks()
  const link = links.find((row) => row.steamId === steamId)
  return link ? link.userId : null
}

/**
 * A grant the game holds and the site does not. If a grant that reaches this
 * server was only kept off it by an EXCEPTION, the exception is what the game
 * just undid, so the exception goes. Otherwise a Steam-account grant for this
 * server alone is written (D188, D190).
 */
async function adoptGrant(serverId, { steamId, permission, source }) {
  const exceptions = (await db.listExceptions()).filter((e) => e.serverId === serverId)

  if (exceptions.length) {
    const userId = await userOf(steamId)
    const [userGrants, steamGrants] = await Promise.all([
      userId === null ? [] : db.listGrants({ userId }),
      db.listSteamGrants({ steamId }),
    ])

    const candidates = [
      ...userGrants.map((g) => ({ holder: 'user', id: g.id, permission: g.permission, scope: g.scope })),
      ...steamGrants.map((g) => ({ holder: 'steam', id: g.id, permission: g.permission, scope: g.scope })),
    ].filter((g) => model.normaliseName(g.permission) === permission && model.inScope(g.scope, serverId))

    for (const grant of candidates) {
      const exception = exceptions.find((e) => e.holder === grant.holder && Number(e.grantId) === Number(grant.id))
      if (exception) {
        await db.deleteException(exception.id)
        return
      }
    }
  }

  await db.insertSteamGrant({ steamId, permission, scope: serverId, source })
}

/**
 * A grant the site holds and the game no longer does. Each source that put it
 * on this server stops doing so: one scoped to this server alone is deleted; one
 * that reaches further gains an exception here. An event's grant is left to the
 * event (the reconciler never sends one here).
 */
async function dropGrant(serverId, { sources = [] }) {
  for (const source of sources) {
    if (source.type !== 'userGrant' && source.type !== 'steamGrant') continue

    const holder = source.type === 'userGrant' ? 'user' : 'steam'

    if (source.scope === serverId) {
      if (holder === 'user') await db.deleteGrant(source.id)
      else await db.deleteSteamGrant(source.id)
    } else {
      await db.addException({ holder, grantId: source.id, serverId })
    }
  }
}

/** Run one op. Returns a short line for the log. */
async function applyOp(serverId, op) {
  switch (op.op) {
    case 'adoptGroup': {
      // A group of this name may already exist on another server, or be shared
      // with every server but this one: either way this server gets its own.
      const existing = await groupOn(op.name, serverId)
      if (existing) return `group ${op.name}: already the site's`

      const id = await db.insertGroup({ name: op.name, title: op.title, rank: op.rank, parent: op.parent, source: op.source })
      await db.setGroupServers(id, { allServers: false, servers: [serverId] })
      return `group ${op.name}: adopted`
    }

    case 'setGroupAttrs': {
      const group = await ownGroup(op.group, serverId)
      if (!group) return `group ${op.group}: not the site's`
      await db.updateGroup(group.id, { title: op.title, rank: op.rank, parent: op.parent })
      return `group ${op.group}: title, rank and parent from the game`
    }

    case 'adoptGroupPermission': {
      const group = await ownGroup(op.group, serverId)
      if (!group) return `group ${op.group}: not the site's`
      await db.addGroupPermission(group.id, op.permission)
      return `group ${op.group} + ${op.permission}`
    }

    case 'dropGroupPermission': {
      const group = await ownGroup(op.group, serverId)
      if (!group) return `group ${op.group}: not the site's`
      await db.removeGroupPermission(group.id, op.permission)
      return `group ${op.group} − ${op.permission}`
    }

    case 'adoptMember': {
      const group = await ownGroup(op.group, serverId)
      if (!group) return `group ${op.group}: not the site's`
      await db.addGroupSteamMember(group.id, op.steamId, { source: op.source })
      return `${op.steamId} in ${op.group}`
    }

    case 'dropMember': {
      const group = await ownGroup(op.group, serverId)
      if (!group) return `group ${op.group}: not the site's`

      // Whichever way the site had them in it: as a Steam account, and as the
      // website account that account is linked to.
      await db.removeGroupSteamMember(group.id, op.steamId)
      const userId = await userOf(op.steamId)
      if (userId !== null) await db.removeGroupMember(group.id, userId)
      return `${op.steamId} out of ${op.group}`
    }

    case 'adoptGrant':
      await adoptGrant(serverId, op)
      return `${op.steamId} + ${op.permission}`

    case 'dropGrant':
      await dropGrant(serverId, op)
      return `${op.steamId} − ${op.permission}`

    case 'dropGroup': {
      const group = await groupOn(op.group, serverId)
      if (!group) return `group ${op.group}: not the site's`

      const groupServers = await db.listGroupServers()
      if (model.isShared(group, model.serversByGroup(groupServers))) {
        await db.removeGroupFromServer(group.id, serverId)
        return `group ${op.group}: no longer on ${serverId}`
      }

      await db.deleteGroup(group.id)
      return `group ${op.group}: deleted`
    }

    default:
      return `unknown op ${op.op}`
  }
}

/** Run a plan's ops in order. One op failing does not stop the rest. */
async function applyOps(serverId, ops, log = null) {
  const done = []

  for (const op of ops) {
    try {
      // eslint-disable-next-line no-await-in-loop
      done.push(await applyOp(serverId, op))
    } catch (err) {
      done.push(`${op.op} failed: ${err.message}`)
      if (log) log.warn('permission op failed', { server: serverId, op: op.op, error: err.message })
    }
  }

  return done
}

module.exports = { groupOn, ownGroup, applyOp, applyOps }